A shader stack is like transparent sheets laid on top of one another. Earlier entries sit at the bottom and later ones sit above them, so changing the order changes what is covered and how colors combine.
The order of entries in `layers` is the draw order. Lower `opacity` lets earlier layers show through, while `blendMode` changes how colors combine. Use `visible: false` when a layer should not draw but still needs to be referenced.
Effects such as blur or color adjustment process layers drawn before them, so put an effect after its input. If it comes first, there may be nothing to change; stacking too many layers also makes the source of a visual change harder to spot.
When to use
Use it to combine a gradient and particles in a hero background, add blur or color adjustment over an image, or control which visual sits in front. A stack is unnecessary when one layer or a single static image is enough.